Hydraulic jacks

Abstract

The invention relates to hydraulic jack operating systems. The end-of-stroke damping of the jack is produced by an element of the shape of a truncated cone, integral with the stem of the jack, which penetrates into a floating ring and which defines, in this ring, a damping chamber isolated from the remainder of the capacity of the jack. When the stem of the jack makes its return movement, the chamber is re-supplied with oil through passages which were previously obturated by the displacement of the ring at the instant of the damping. The invention is applicable to high speed hydraulic controls for circuit breakers with ultra-rapid operation.

I claim 
     
       1. Hydraulic jack with incorporated end-of-stroke damping device in which the piston is provided with at least one first damping component presenting a male element cooperating, at one of the ends of stroke, with a second damping component constituted by a ring floatingly mounted within a seating provided in the jack cylinder, said seating making possible radial wobbling of said ring, while the inner surface of said ring defines with the outer surface of said male element an annular clearance of variable section for the throttling of the hydraulic fluid, which hydraulic fluid, in the course of end-of-stroke damping, leaks from an annular chamber of variable volume, or damping chamber, delimited, in the axial direction, by an annular radial surface of said ring and by the opposed annular radial surface of the first component, said seating also making possible limited axial wobbling of said ring; said ring being hollowed out by through-going passages for re-supply of said damping chamber, said passages being hollowed out substantially parallel to the axis of the jack; and, in the damping condition, said passages are obturated, as a result of axial displacement of the ring, so as to isolate the damping chamber and render same independent of the remainder of the capacity of the jack, while, on return of the piston in the opposite direction after damping, said passages are freed so as to put the damping chamber into communication with the remainder of the capacity of the jack with the object of re-supplying said chamber with hydraulic fluid. 
     
     
       2. Hydraulic jack as set forth in claim 1, in which said passages are constituted by slots hollowed out in the periphery of the damping ring. 
     
     
       3. Hydraulic jack as set forth in claim 1, in which said passages are constituted by ducts pierced through the ring. 
     
     
       4. Hydraulic jack as set forth in claim 1, in which said passages open, at one of their ends, opposite a stationary annular surface integral with the jack and constituting the extreme wall of said seating against which the ring bears in the course of the damping in order to close in a fluid-tight manner said end of the passages and, at the other of their ends, said passages open into the damping chamber, opposite said opposed annular radial surface of the first component. 
     
     
       5. Hydraulic jack as set forth in claim 1, in which said first damping component comprises a male element associated with an intermediate element interposed between said male element and the piston of the jack, said intermediate element sliding with relative fluid-tightness in the jack cylinder. 
     
     
       6. Hydraulic jack as set forth in claim 5, in which said intermediate element is hollowed out by a groove and ducts for evacuation of leakages coming from the damping chamber. 
     
     
       7. Hydraulic jack as set forth in claim 6, in which a duct for directly re-supplying the passages is provided in a selected one of the component parts, cylinder and bottom, of the jack, said duct opening out near the surface of the ring situated opposite said stationary annular surface of the jack. 
     
     
       8. Hydraulic jack as set forth in claim 7, in which the duct for re-supplying the passages, located at one side of said ring, also constitutes the supply duct for the corresponding chamber of the jack, said ring being pierced by ducts of large section in direct communication with said corresponding chamber but not in communication with the damping chamber. 
     
     
       9. Hydraulic jack as set forth in claim 8 and of the differential double-acting type; in which it contains a damping system for each of the ends of stroke; the ducts for supply and evacuation of one of the chambers of the jack open into an annular clearance defined between the cylinder of the jack and an external jacket surrounding said cylinder, said clearance being connected to means for supply and reception of hydraulic fluid under pressure. 
     
     
       10. Hydraulic jack as set forth in claim 9 in which the stem of the jack is coupled to the movable contact of an electric circuit breaker.